This disclosure relates to fuel tank systems, and in particular to fuel tank vapor management systems.
This disclosure relates to fuel tank systems, and in particular to fuel tank vapor management systems.
It is recognized that fuel vapors within fuel tanks become combustible in the presence of oxygen. An inerting system decreases the probability of combustion of flammable materials stored in a fuel tank by maintaining a chemically non-reactive or inert gas, such as nitrogen-enriched air, in the fuel tank gas space also known as ullage. Three elements are required to initiate and sustain combustion: an ignition source (e.g., heat), fuel, and oxygen. Combustion may be prevented by reducing any one of these three elements. If the presence of an ignition source cannot be prevented within a fuel tank, then the tank may be made inert by: 1) reducing the oxygen concentration, 2) reducing the fuel concentration of the ullage to below the lower explosive limit (LEL), or 3) increasing the fuel concentration to above the upper explosive limit (UEL). Many systems reduce the risk of combustion by reducing the oxygen concentration by introducing an inert gas such as nitrogen-enriched air (NEA) to the ullage, thereby displacing air with a mixture of nitrogen and oxygen at target oxygen thresholds for avoiding explosion or combustion.
It is known in the art to equip aircraft with onboard inert gas generating systems, which supply nitrogen-enriched air to the gas space (i.e., ullage) within the fuel tank. The nitrogen-enriched air has a substantially reduced oxygen content that reduces or eliminates combustible conditions within the fuel tank. However, conventional fuel tank vapor management systems do not address egress of volatile fuel vapors from the fuel tank gas space or their impact on safety or environmental concerns, nor do they address ingress to the tank of potentially problematic gases such as water vapor.